Mountain Gorilla, Rwanda. About 880 mountain gorillas, who have thicker and more fur than other great apes, live in forests high in the mountains in the Congo Basin. They are threatened by civil conflict, poaching, and an encroaching human population.Panoramic Images/Getty Images

Mountain Gorilla, Rwanda. About 880 mountain gorillas, who have thicker and more fur than other great apes, live in fo

See 17 Animals on the Verge of Going Extinct

More than 10,000 species—everything from the Asian Elephant to the Bluefin tuna—have earned a place on the list of endangered animals, according to the International Union for Conservation of Nature.

But a select group of endangered species face an even greater threat. Animals in this group, included in the galley above, have been labelled "critically endangered" and teeter on the brink of extinction.

The threats faced include everything from deforestation to climate change. And, conservationists say, any effort to save endangered animals must deal with the surrounding issues to sustain itself. The annual Endangered Species Day—recognized on May 20—is a great place to start.